1. Field of the Invention
This invention relates generally to a kit for the temporary construction of a variety of three-dimensional models and designs. More particularly, this invention relates to a construction set to be used as an educational tool or toy for children, or as a scale model planning tool. The kit comprises a resilient base with a plurality of intersecting slots, and a plurality of slats that may be inserted into and removed from the slots. The slots are formed such that the slot-widening which is caused by insertion of the slats is effected primarily by the shear associated with a lateral displacement of the intra-slot base material rather than by a crushing of the material. The base material itself is formed of a resilient foam such that upon removal of a slat the lateral displacement is removed along with the small compression that may have occurred, thus re-establishing the narrow slot. Still more particularly, when the kit is used as an educational tool to illustrate the effects of gravity, friction, and other related physical principles, the base is oriented in a quasi-vertical fashion and the slats configured so as to provide both horizontal and vertical surfaces which in turn define pathways along which rollable objects can traverse under the forces of gravity.
2. Description of Prior Art
Scale model construction kits have been designed for many years to assist in visualizing the size, shape and arrangement of rooms and/or buildings. Architects consider them advantageous tools, providing a better understanding of two-dimensional plans. Building planners use them to arrange furniture and equipment in preexisting and future spaces. One example of this type of construction set is presented in U.S. Pat. No. 4,650,437 issued to Sitkus (1987). These kits may also be used as educational toys for children. See for example U.S. Pat. No. 4,270,302 issued to Dandia (1981).
Both patents noted above disclose construction sets which generally comprise a horizontal base unit into which vertical members are inserted. This is the form of most construction sets. In particular, the base is commonly grid-like and the vertical members are fitted into grooves, slots, or something similar within the grid system. The vertical members can be moved to various positions on the base because they are not permanently attached to it. Typically, a tight fit between the vertical members and the grooves is all that is necessary to hold a three-dimensional model in place. The vertical members can thus be maintained in position without extraneous attachment means. This is an important feature and a necessary one if the set is to be used in visualizing a variety of configurations.
As will be discussed in more detail in the following paragraphs, there are two problems associated with the construction sets of past and current design: 1) the size of the groove or slot in the gridwork of the base increases with repetitive insertion and removal of vertical members, caused by forcing the vertical member into place and "wiggling" to extract it, resulting in a significant crushing of the base material defining the slot and hence in an increasingly loose fit and easy displacement of the vertical member over a period of time; and 2) the materials used in the fabrication of construction sets, typically wood, rigid plastics and even metal, are susceptible to chipping and/or splintering, which may render the set useless, and, in the case of a toy construction set, dangerous.
It is because the construction sets currently available are made of wood, metal or a rigid plastic that they have little or no "memory." This memory is the ability of a material to return to its original shape and dimensions after a strain-producing force has been applied to it. Relating to construction sets, such a force occurs when the vertical member is placed in the grid system of the base. At that interface, the vertical member, which by the nature of the assembly must be slightly thicker than the groove width, exerts an outward force on the material of the base and the grid exerts a correponding inward force on the section of the vertical member that it contacts. The force on the vertical member compresses it; the force on the grid material comprising the walls of the grooves expands the size of those grooves as the result of a combined compressional/shear strain. In traditional systems, the balance of strain is in the direction of compression, with the result that over a period of time the forces acting on the grid material comprising the walls of the grooves create a permanent change or "compression set" in the base material. The exact details of this compression set are dependent upon the length of time the force is applied and the characteristics of the material(s) involved; nevertheless, it is an endemic problem with traditional systems, leading inexorably to a loss of slot-retention capacity.
Because it is a particular feature of these construction sets that room/building arrangements can be easily varied, insertion and extraction of the vertical members occurs often. The first time a vertical member is placed in a groove, the fit is the tightest. Repetition of the process results in progressively looser fits, due to the thickness reduction of the vertical member and/or width increase of the grooves. At that time the construction set becomes unusable because the three-dimensional model can no longer be maintained in place.
Another problem associated with the metal, wooden, and other rigid construction sets, is the susceptibility of the material to splinter or fracture. This may occur when the vertical member is inserted into or removed from the groove, or it may be caused by incidental contact with a destructive force. Depending upon the location of the splinter or fracture, one or more components of the set may become unusable. Splinters and fractures may be particularly dangerous when a child is using the set to arrange a variety of three-dimensional designs and removal and insertion of vertical members happens on a regular basis.
The prior art of construction sets has failed to address the need to fabricate these sets of a material with good memory (that is, little or no compression set), tough enough not to splinter or fracture, and yet rigid enough to maintain the vertical and base components in position. For example, French Patent No. 524,064 issued to Girlot (1921) discloses a construction game the novelty of which is embodied in its capability to provide a realistic scale-model of stable fabrication. It comprises vertical panels and a base into which crisscrossing grooves are scored. The vertical members slide into the grooves and are then locked into position with an additional component. It teaches that the base may be made of wood or any other suitable material, such as cardboard. It fails to identify the-problems associated with wooden construction sets, i.e. a lack of memory and susceptibility to splintering. Although sliding the vertical members into place indicates memory may not be required for this particular set, locking the vertical members into place using additional parts is a complicating feature which reduces the desired simplicity of these types of construction sets, particularly when the user is a child.
U.S. Pat. No. 2,883,764 issued to Stephens (1959) discloses a means for designing and laying out plans for buildings, comprising a base with slots into which vertical members are inserted. The vertical members must be fitted into the slots to produce a scale model construction. U.S. Pat. No. 2,023,300 issued to Barnett (1934) describes a re-arrangeable toy model set comprising a grid-like base and removable vertical members. However, the components are made of wood or solid rubber and a mallet must be used to secure the vertical members in place. Both Stephens and Barnett fail to address the importance of fabricating the components of the model set from a material that recovers after force has been applied and which does not splinter or fracture. Furthermore, the need to have a supplemental tool to fit the vertical members into the grid, as indicated by Barnett, is undesirable when the device is to be used by young children wherein such tools add to the complication and may be easily lost over a period of time.
U.S. Pat. No. 4,400,906 issued to Bove (1983) is also for a construction set. It describes a set containing a base with a grid-like set of mortises or tenons into which partition modules are inserted. The disclosure states that the mortises may be molded or calendered and the tenons may be machined. This instruction indicates Bove has failed to address the problems associated with the current materials of choice. As further stated by Bove, the dimensions and distribution of the mortises and tenons must be determined precisely. To do so, the material used for the base must be metal, wood, or a rigid plastic. This teaches away from the need for a resilient material, that is, one with good memory, because a resilient material is unsuitable for machining to precise dimensions.
Toy products fabricated of resilient foam have been described in the past. See, for example, U.S. Pat. No. 3,822,499 issued to DeVos (1974) and U.S. Pat. No. 3,280,499 issued to Studen (1966). Both patents disclose products made of polymeric foam material wherein the materials used avoid the problems of fracturing and splintering. In addition, both patents note the advantages of using a material with memory. Nevertheless, the DeVos and Studen disclosures fail to address the problems associated with the usage of foam materials in a grid base for a rearrangeable three-dimensional design. Specifically, while polymeric materials all have memory to varying degrees, all will eventually "set" when the material is compressed. The extent of the set is dependent upon the material and the length of time it is under load. When the object of an invention is to provide a grid system for repeated insertion and removal of vertical members, it is essential to minimize if not eliminate set of the base component. Thus, while the use of a resilient material, and even a resilient foam material, is important to kit longevity, it is particularly important to combine that characteristic with a grid design that complements and takes advantage of the material's resiliency.
Prior systems utilizing resilient/foam materials as the base component in rearrangeable toy construction devices include those described in patents issued to Mengeringhausen, U.S. Pat. No. 3,286,391 (1964) and Walsh, U.S. Pat. No. 4,758,195 (1988). Both disclosures note the advantage of using either a resilient or resilient-foam material with receptacles into which rigid components may be inserted and then removed. Both disclosures fail, however, to note that even these materials, used in the ways described, will develop a compression set that ultimately comes from repeated insertion and removal. Therefore, what is needed is a resilient foam material to be used in a grid base design that overcomes problems associated with compression set. What is also needed is a rearrangeable grid system with a base component that is fabricated of a material with memory, toughness and yet sufficient rigidity such that: 1) repetitive insertion and extraction of removable components will not result in a loose fit of those components; and 2) splintering and/or chipping of the components will not occur.
In addition to the general problems associated with prior construction sets, there are additional problems associated with rollways and other similar devices that teach children about basic physical principles. Most of these types of prior construction sets have been designed to assist children in forming shapes, toys and building models. Although some may be adapted for use as tools to assist children in comprehending such principles as gravity, momentum, friction, acceleration and others, not one is capable of illustrating such principles on a scale suitable for children. Furthermore, prior devices used for this purpose generally fail to permit a child to alter the means by which these principles can be illustrated. This failure relates to an essentially complete breakdown of the device when one or more components of the device are removed for alteration of pathways and the like formed by a plurality of components. This is a problem of particular concern when the user is a young child and it becomes difficult to reform a pathway when a component has been removed. Also, the prior devices generally available are not designed to withstand the impact and weight associated with rollable and slidable objects suitable for illustration of the effects of gravity, friction and the like. Therefore, what is needed is a changeable, or rearrangeable grid system which permits a child to proceed at his or her own pace in discovering and exploring basic forces. What is also needed is a changeable grid system kit wherein the components of the system are easily reconfigured with out a complete breakdown of the system itself. Furthermore, what is needed is an educational changeable grid system designed to withstand the impact and loading associated with rollable and slidable objects of a size suitable to illustrate the basic forces described herein.